Adenoviral-Mediated Modulation of Sim1 Expression in the Paraventricular Nucleus Affects Food Intake (original) (raw)
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Adenovirus-mediated suppression of hypothalamic glucokinase affects feeding behavior
Scientific reports, 2017
Glucokinase (GK), the hexokinase involved in glucosensing in pancreatic β-cells, is also expressed in arcuate nucleus (AN) neurons and hypothalamic tanycytes, the cells that surround the basal third ventricle (3V). Several lines of evidence suggest that tanycytes may be involved in the regulation of energy homeostasis. Tanycytes have extended cell processes that contact the feeding-regulating neurons in the AN, particularly, agouti-related protein (AgRP), neuropeptide Y (NPY), cocaine- and amphetamine-regulated transcript (CART) and proopiomelanocortin (POMC) neurons. In this study, we developed an adenovirus expressing GK shRNA to inhibit GK expression in vivo. When injected into the 3V of rats, this adenovirus preferentially transduced tanycytes. qRT-PCR and Western blot assays confirmed GK mRNA and protein levels were lower in GK knockdown animals compared to the controls. In response to an intracerebroventricular glucose injection, the mRNA levels of anorexigenic POMC and CART a...
Ablation of Sim1 Neurons Causes Obesity through Hyperphagia and Reduced Energy Expenditure
PLOS One, 2012
Single-minded 1 (Sim1) is a transcription factor necessary for development of the paraventricular nucleus of the hypothalamus (PVH). This nucleus is a critical regulator of appetite, energy expenditure and body weight. Previously we showed that Sim1 +/2 mice and conditional postnatal Sim1 2/2 mice exhibit hyperphagia, obesity, increased linear growth and susceptibility to diet-induced obesity, but no decrease in energy expenditure. Bilateral ablation of the PVH causes obesity due to hyperphagia and reduced energy expenditure. It remains unknown whether Sim1 neurons regulate energy expenditure. In this study, Sim1cre mice were bred to homozygous inducible diphtheria toxin receptor (iDTR) mice to generate mice expressing the simian DTR in Sim1 cells. In these mice, Sim1 neuron ablation was performed by intracerebroventricular (ICV) injection of diphtheria toxin. Compared to controls, mice with Sim1 neuron ablation became obese (with increased fat mass) on a chow diet due to increased food intake and reduced energy expenditure. In postinjection mice, we observed a strong inverse correlation between the degree of obesity and hypothalamic Sim1 expression. The reduction in baseline energy expenditure observed in these mice was accompanied by a reduction in activity. This reduction in activity did not fully account for the reduced energy expenditure as these mice exhibited decreased resting energy expenditure, decreased body temperature, decreased brown adipose tissue temperature, and decreased UCP1 expression suggesting an impairment of thermogenesis. In injected mice, hypothalamic gene expression of Sim1, oxytocin (OXT) and thyrotropin releasing hormone (TRH) was reduced by about 50%. These results demonstrate that Sim1 neurons in adult mice regulate both food intake and energy expenditure. Based on the body of work in the field, feeding regulation by Sim1 neurons likely occurs in both the PVH and medial amygdala, in contrast to energy expenditure regulation by Sim1 neurons, which likely is localized to the PVH.
Journal of Neuroscience, 2007
It is well known that neuropeptide Y (NPY) increases food intake. The hypothalamic paraventricular nucleus (PVN) and the lateral hypothalamus (LH) are both involved in the acute, hyperphagic effects of NPY. Although it is obvious that increased energy intake may lead to obesity, it is less understood which aspects of feeding behavior are affected and whether one or multiple neural sites mediate the effects of long-term increased NPY signaling. By long-term overexpressing NPY in either the PVN or the LH, we uncovered brain site-specific effects of NPY on meal frequency, meal size, and diurnal feeding patterns. In rats injected with adeno-associated virus-NPY in the PVN, increased food intake resulted from an increase in the amount of meals consumed, whereas in rats injected in the LH, increased food intake was attributable to increased meal size. Interestingly, food intake and body weight gain were only temporarily increased in PVN-injected rats, whereas in LH-injected rats hyperphagia and body weight gain remained for the entire 50 d. Moreover, in LH-NPY rats, but not in PVN-NPY rats, diurnal rhythmicity with regard to food intake and body core temperature was lost. These data clearly show that the NPY system differentially regulates energy intake and energy expenditure in the PVN and LH, which together adjust energy balance.
Human Molecular Genetics, 2001
The bHLH-PAS transcription factor SIM1 is required for the development of the paraventricular nucleus (PVN) of the hypothalamus. Mice homozygous for a null allele of Sim1 (Sim1-/-) lack a PVN and die perinatally. In contrast, we show here that Sim1 heterozygous mice are viable but develop early-onset obesity, with increased linear growth, hyperinsulinemia and hyperleptinemia. Sim1 +/mice are hyperphagic but their energy expenditure is not decreased, distinguishing them from other mouse models of early-onset obesity such as deficiencies in leptin and melanocortin receptor 4. Quantitative histological comparison with normal littermates showed that the PVN of Sim1 +/mice contains on average 24% fewer cells without a selective loss of any identifiable major cell type. Since acquired lesions in the PVN also induce increased appetite without a decrease in energy expenditure, we propose that abnormalities of PVN development cause the obesity of Sim1 +/mice. Severe obesity was described recently in a patient with a balanced translocation disrupting SIM1. Pathways controlling the development of the PVN thus have the potential to cause obesity in both mice and humans.
Inducible neuronal inactivation of Sim1 in adult mice causes hyperphagic obesity
2014
Germline haploinsufficiency of human or mouse Sim1 is associated with hyperphagic obesity. Sim1 encodes a transcription factor required for proper formation of the paraventricular (PVN), supraoptic, and anterior periventricular hypothalamic nuclei. Sim1 expression persists in these neurons in adult mice, raising the question of whether it plays a physiologic role in regulation of energy balance. We previously showed that Sim1 heterozygous mice had normal numbers of PVN neurons that were hyporesponsive to melanocortin 4 receptor agonism and showed reduced oxytocin expression. Furthermore, conditional postnatal neuronal inactivation of Sim1 also caused hyperphagic obesity and decreased hypothalamic oxytocin expression. PVN projections to the hindbrain, where oxytocin is thought to act to modulate satiety, were anatomically intact in both Sim1 heterozygous and conditional knockout mice. These experiments provided evidence that Sim1 functions in energy balance apart from its role in hypothalamic development but did not rule out effects of Sim1 deficiency on postnatal hypothalamic maturation. To address this possibility, we used a tamoxifen-inducible, neural-specific Cre transgene to conditionally inactivate Sim1 in adult mice with mature hypothalamic circuitry. Induced Sim1 inactivation caused increased food and water intake and decreased expression of PVN neuropeptides, especially oxytocin and vasopressin, with no change in energy expenditure. Sim1 expression was not required for survival of PVN neurons. The results corroborate previous evidence that Sim1 acts physiologically as well as developmentally to regulate body weight. Inducible knockout mice provide a system for studying Sim1's physiologic function in energy balance and identifying its relevant transcriptional targets in the hypothalamus.
Sustained NPY Overexpression in the PVN Results in Obesity via Temporarily Increasing Food Intake
Obesity, 2009
short communications nature publishing group integrative Physiology Long-term central administration of neuropeptide Y (NPY) results in an obese phenotype, characterized by hyperphagia, increased lipogenesis in liver and adipose tissue, and elevated plasma concentrations of leptin, insulin, and corticosterone (1-4). Obesity is also induced when NPY is overexpressed in the adult hypothalamus of mice after hypothalamic injections of recombinant adeno-associated viral (rAAV) particles (5). Recently, we have shown (with the use of rAAV-NPY injected at the site of NPY receptors in the paraventricular nucleus (PVN)) that increased NPY signaling in the rat PVN is sufficient to result in obesity (6,7).
Sim1 gene dosage modulates the homeostatic feeding response to increased dietary fat in mice
American Journal of Physiology-Endocrinology and Metabolism, 2004
Haploinsufficiency of the transcription factor gene Sim1 has been previously implicated in hyperphagic obesity in humans and mice. To investigate the relation between Sim1 dosage and hyperphagia, we generated sim1-knockout mice and studied their growth and feeding behavior. Heterozygous mice weaned on standard chow consumed 14% more food per day than controls and developed obesity, hyperinsulinemia, and hyperleptinemia. The sim1 heterozygous mice were also significantly longer than controls. Heterozygous animals had modestly increased feeding efficiency, suggesting reduced energy expenditure, but voluntary wheel-running activity did not differ significantly between the two groups. We studied the effect of dietary fat on the feeding behavior of heterozygous sim1 mutant mice. The tempo and severity of weight gain were much greater in animals weaned on a high-fat diet. When acutely challenged with increased dietary fat, sim1 heterozygous mice weaned on the chow diet markedly increased ...
Overexpression of CART in the PVN Increases Food Intake and Weight Gain in Rats
Obesity, 2008
Objective: Cocaine- and amphetamine-regulated transcript (CART) codes for a hypothalamic neuropeptide, CART (55–102), which inhibits food intake. Intracerebroventricular injection of CART (55–102) reduces appetite, but also results in motor abnormalities. More recently, studies have demonstrated that administration of CART directly into the paraventricular nucleus (PVN) increases food intake. To investigate the role of CART in the regulation of energy balance in the PVN, we used recombinant adeno-associated virus (rAAV) to overexpress CART in the PVN.Methods and Procedures: Male Wistar rats were injected with either rAAV-encoding CART (rAAV-CART) or rAAV-encoding enhanced green fluorescent protein (rAAV-EGFP) as a control. Food intake and body weight were measured regularly. Animals were fed on normal-chow diet for the first 93 days of the study. After this point, they were fed on high-fat diet. Animals were killed 138 days postinjection and blood and tissues were collected for analysis.Results: Overexpression of CART in the PVN resulted in increased cumulative food intake and body weight gain compared with rAAV-EGFP controls when fed normal chow. These changes became significant at day 65 and 79, respectively and were accentuated on a high-fat diet. A 4% increase in food intake was observed in rAAV-CART animals on a normal-chow diet and a 6% increase when fed a high-fat diet. At the end of the study, rAAV-CART-treated animals had higher circulating leptin concentrations in accord with their higher body weight.Discussion: These data provide further evidence that hypothalamic CART plays an orexigenic role.
Programmed hyperphagia secondary to increased hypothalamic SIRT1
Brain research, 2014
Small for gestational age (SGA) offspring exhibit reduced hypothalamic neural satiety pathways leading to programmed hyperphagia and adult obesity. Appetite regulatory site, the hypothalamic arcuate nucleus (ARC) contains appetite (NPY/AgRP) and satiety (POMC) neurons. Using in vitro culture of hypothalamic neuroprogenitor cells (NPC) which form the ARC, we demonstrated that SGA offspring exhibit reduced NPC proliferation and neuronal differentiation. bHLH protein Hes1 promotes NPC self-renewal and inhibits differentiation by repressing neuronal differentiation genes (Mash1, neurogenin3). We hypothesized that Hes1/Mash1 and ultimately ARC neuronal differentiation and expression of NPY/POMC neurons are influenced by SIRT1 which is a nutrient sensor and a histone deacetylase. Control dams received ad libitum food, whereas study dams were 50% food-restricted from pregnancy day 10 to 21 (SGA). In vivo studies showed that SGA newborns and adult offspring had increased protein expression ...
Feeding induced changes in the hypothalamic transcriptome
Clinica Chimica Acta, 2009
Background: Obesity is a complex multifactorial disorder which needs a comprehensive approach for prevention and treatment. We investigated the modifications in the hypothalamic gene expression induced by high-fat (HF) and low-fat (LF) meal ingestion in mice, in order to identify the signals rapidly mediating the hypothalamic control on energy intake. Methods: After fasting, 1 group of mice was sacrificed and the others were fed ad libitum with HF or LF diet, and sacrificed 3 h after the beginning of the meal. The hypothalamus was sampled and the serial analysis of gene expression method was performed. Results: Approximately 254,588 tags, which correspond to 65,548 tag species were isolated from the 3 groups. The data showed twelve transcripts regulated by food intake. Among these, 2 transcripts have mitochondrial functions (MtCo1, Ppid), 3 are involved in protein transport and regulation (Ube2q2, Mup1, Sec13), 1 in cellular pH control (Slc4a3) and another 1 has a role in the epigenetic control of gene expression (Setd3). In addition, 5 potentially novel transcripts were differentially modulated. Conclusion: We identified genes that may regulate hypothalamic circuits governing the early response to food intake. 3 genes were specifically modulated by high-fat intake.